Process and bath for pickling metals



252. COMPOSITIONS,

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Patented June 1 8, 1935 UNITED STATES Examiner- PATENT OFFICE PROCESS AND BATH FOR PICKLING LIETALS Vanderveer Voorhees, Hammond, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing.

Application November 28, 1931,

Serial No. 571,859.

7 Claims.

v comprising a mixture of organic bases of nitrogenous character.

I have found that the organic bases prepared from the above sources are effective in reduc ing the attackoLacids upon metals. For example, they have a remarkabl'fiect in retarding the rate of corrosion of iron and steel and other metals by acids without substantial eifect upon the rate of attack on oxides of iron. On this account they may be used in pickling metals, particularly ferrous metals. As an indication of this effect it may be stated that two baths of 5% sulfuric acid were prepared. To one bath 0.135 gram of free organic bases was added per liter. Strips of clean sheet iron were immersed in both baths which were maintained at about F'. During the period of ten minutes the strips immersed in the pure acid suffered a corrosion loss of 27.5 milligrams per square inch, while a strip immersed in similar acid to which the organic bases had been added had a corrosion loss of only about 8 milligrams per square inch.

The effect of these organic bases in reducing the attack of acids on metals is exhibited by pickling baths of wide ranges of concentration and with wide ranges of added bases. Satisfactory results may be obtained when the concentration of the bases is as low as 0.08 gram per liter and as high as 5 grams per liter. The specific figures given are illustrative only, and are intended to set forth a specific pickling bath suitable for commercial utilization.

Mineral oils nrepg ed frorn shale, peat or lignite are agitated or contacted with about .05 to 0.8 pound of 50% sulfuric acid per gallon of oil, and the acid layer is permitted to settle and is then withdrawn. The acid solution is then completely neutralized with a base such as sodium hydroxide or lime and the free organic bases are recovered therefrom. The free organic bases separate as an oily layer on the surface of the solution after the neutralization step, and

may be removed by decantation or other suitable means.

Instead of using sulfuric acid, I may agitate or contact the oil with sulfur dioxide at relatively low temperatures, i. e. 10 F., settle the sulfur dioxide extract from the main body of oil, then remove the sulfur dioxide from the dissolved fraction by heating said fraction until the sulfur dioxide has evaporated. The remaining complex mixture or organic bases and oily products may be used for pickling agents without further treatment. However, the organic bases are preferably removed from the mixture of bases and oily products by extracting with dilute sulfuric acid. The acid should be used in concentrations in excess of the amount needed to react with the organic bases. The acid layer is removed from the oily materials and may be used as a pickling agent without further purification. If desired, the free bases may be recovered from this acid extract by neutralizing the acid with an aqueous solution of alkali and removing the oily fraction of bases by decantation or other suitable means. The free organic bases so prepared may be used as inhibitors for pickling baths. The above processes for preparing free bases are well known and do not constitute a part of my invention.

As a specific example of preparing the bases, crude shale distillate is agitated with about 0.4 pound of 50% sulfuric acid per gallon of oil and the acid layer is settled out and withdrawn. The acid layer is then completely neutralized with a strong base such as sodium hydroxide, whereupon the free organic bases separate as an oily layer on the surface of the solution and may be removed therefrom by decantation.

If desired, the organic bases may be removed from the neutralized solution by distillation with steam, or by extraction with a suitable solvent such as na htha or the like, the organic bases being recovere from the extraction liquid by fractional distillation. The latter methods are particularly suitable where lime is used to neutralize the sulfuric acid, since in that case there is a tendency for the oily bases to become emulsified, rendering separation by decantation diflicult and incomplete.

' Also a suitable fraction of organic bases can be prepared by extracting the shale rock with sulfuric acid or sulfur dioxide after the distillable oil has been removed therefrom. The acid solution is treated as above described to recover the free organic bases. The term shale oils is used in the claims to define the oils derived from shale,

peat, lignite and related oil bearing minerals and is not used to include petroleum oils.

This application is a continuation-in-part of my co-pending application No. 247,747, filed January 16, 1928.

Although the present invention has been described in connection with the details of specific embodiments thereof, it is not intended that the specific details shall be regarded as limitations upon the scope of the invention.

I claim:

1. A pickling bath comprising a dilute acid and a relatively small quantity of organic bases separated from shale oil.

2. The method of acid pickling metals which comprises subjecting the metal to the action of an acid pickling bath in which has been incorporated free organic bases separated from shale oil.

3. The method of acid pickling metals which comprises subjecting the metal to the action of an acid pickling bath in which has been incorporated organic bases separated from shale oils.

4. The method of acid pickling metals which comprises subjecting the metal to the action of an acid pickling bath in which has been incorporated a dilute acid solution of organic bases separated from shale oils.

5. A bath for removing scale from metal, said bath comprising, a dilute aqueous solution of a mineral acid adapted to attack and remove said scale, and a small quantity of organic bases separated from shale oil.

6. A bath for removing scale from metal, said bath comprising, a dilute solution of sulfuric acid and a relatively small quantity of organic bases separated from shale oil.

7. A bath for removing scale from metal, said bath comprising, an aqueous solution of a mineral acid adapted to attack and remove said scale, and a small quantity of a dilute acid solution of organic bases separated from shale oil.

VANDERVEER VOORHEES. 

